Abstract: In piecoelectric measuring elements comprising two or more crystal elements that are jointly subject to the mechanical variable to be measured and are provided with electrically conductive electrodes on opposite surfaces located essentially normal to the electric (x) axes of these crystal elements, disadvantages arising from shearing stresses can be prevented by using crystal elements (2) from crystals of point group 32, in which exist two opposite types of enantiomorphism, l and r, in which part of the crystal elements used belong to one of the two enantiomorphic types l or r, and have one of the two absolute orientations of the x-axis, .alpha..sub.1 or .alpha..sub.2, while the remaining crystal elements belong to the opposite enantiomorphic type and have the opposite orientation of the x-axis.

Abstract: A pressure measuring instrument for the measurement of the combustion chamber pressure in a cylinder of an internal combustion engine, comprises a piezoelectric pressure sensor. The sensor includes an annular disk-like electrode with an output terminal, a piezoelectric element in contact with said electrode, a pair of annular pressure acting members having interposed therebetween said electrode and said piezoelectric element, and a lead. The piezoelectric pressure sensor is disposed between a first wall on a cylinder head and a second wall of a spark plug.

Abstract: An activity sensor wherein a piezoelement of the flexural type is employed. The activity sensor avoids a depolarization even given great mechanical stresses and simplifies the contacting of such a sensor regardless of the surfaces to which it is applied. It is provided in accord with the invention that the piezoelement is composed of two individual or inter-related piezoceramic parts arranged side-by-side which are oppositely polarized and are provided with electrodes on both sides. On one side, the electrodes are electrically connected to one another and, on the other side, are connected to terminals.

Abstract: Monitoring explosive devices is accomplished with a substantially z-cut lithium niobate crystal in abutment with the explosive device. Upon impact by a shock wave from detonation of the explosive device, the crystal emits a current pulse prior to destruction of the crystal. The current pulse is detected by a current viewing transformer and recorded as a function of time in nanoseconds. In order to self-check the crystal, the crystal has a chromium film resistor deposited thereon which may be heated by a current pulse prior to detonation. This generates a charge which is detected by a charge amplifier.

Abstract: An apparatus for sensing differential pressures is provided. The apparatus includes a housing having an inner chamber filled with an incompressible working fluid. First and second diaphragms are provided in said housing for interacting with the fluids being measured. A flex-tube is provided in the housing and is coupled to one of the diaphragms for sensing the differential pressure. One end of the flex-tube is securely mounted to the housing and the other end is coupled to the diaphragm. A quartz sensor is positioned on the core for sensing strain applied to the flex-tube by the differential pressure exerted on the diaphragm.

Abstract: A new type of pressure sensor is disclosed here. The sensor is composed of a pair of glass substrates and a ferroelectric liquid crystal which is interposed between the substrates and exhibits piezoelectric effect. Because of crystalline property in liquid phase, the piezoelectric medium can be easily disposed and aligned between the substrates in light of the orientation of the surface contiguous to the liquid crystal layer.

Abstract: Laminates of polyvinylidene fluroride (PVDF) are employed as piezoelectric sensors and actuators which can sense and/or generate complex motions that include bending, stretching, and twisting components. The laminates can be attached directly to a mechanical structure whose motions are to be sensed and/or controlled. By skewing the principal axes of each of the lamina in the laminate with respect to one another, the laminate is responsive not only to bending motions, but to torsional motions as well. Surface electrodes are disposed on the top and bottom sides of each of the lamina to either sense voltage generated by the lamina in response to motion imparted thereto, or supply voltage to the lamina to induce motion therein. The shape of the surface electrode patterns can be varied to control the particular components of motion to which each of the lamina is responsive (e.g., bending modes). The polarization profile in each of the lamina can also be varied for this purpose.

Abstract: A transducer for sensing fluid pressure including an enclosure forming housing, a cup-shaped rubber-like mount having an end wall and an annular side wall for supporting a pressure sensing electronic chip against the inner end wall surface of the mount. The chip is supported against the end wall in covering relation to a small opening in the end wall which connects one side of the chip with atmospheric pressure. A layer of non-hardening sealant gel extending between the inner side wall surface completely covers the chip and transmits fluid pressure to a second surface of the chip but inhibits fluid contact and leakage past the chip.

Abstract: A process of bonding crystalline quartz plates in a plate assembly of a quartz crystal resonator is provided. The plate assembly includes a base plate, a resonator plate, a cover plate, a first silver and indium alloy layer between the base plate and the resonator plate, and a second silver and indium alloy layer between the resonator plate and the cover plate. The process of bonding the plates in the plate assembly includes the steps of depositing in sequence on base plate face and on the cover plate face, a layer of chromium, a layer of silver, and a layer if indium, and also includes the steps of depositing in sequence on two opposite faces of the resonator plate, a layer of chromium, and a layer of silver, and also includes the steps in sequence of sandwiching the resonator plate between the base plate and the cover plate to form a plate assembly, then evacuating the plate assembly, compressing the plate assembly, and heating the plate assembly to about 310 degrees centigrade for several hours.

Abstract: A digital integrator for sensors which takes a time varying current or charge flow signal and converts it into a proportional voltage varying signal. The voltage varying signal is then preferably passed through an active full wave rectification subcircuit to provide an absolute value of the time varying voltage signal. The voltage signal also is analyzed by a zero crossing detector. The absolute value signal is converted into a proportional frequency varying signal which is counted either positively or negatively to produce an integral of the current flow with time. The integrator can be used with sensors such as piezoelectric crystals to indicate force on a real-time basis. The integrator is described as part of an animal hoof force detection system.

Abstract: Piezoelectric polymer film, when conformably adhered to inner or outer surfaces of an inflated balloon, functions as a microphone when the pressure of sound waves causes the film to vibrate and generate an electrical signal. The film may be in the form of an helical strip, individual strips electrically serially connected, or may itself form the inflatable material. A receiving device is electrically coupled with the electrodes formed on the piezoelectric film for processing the electrical signals generated by the vibrating piezoelectric polymer film.

Abstract: A structural member having a piezoelectric transmitter film and a piezoelectric receiver film adhered thereto. The transmitter film produces a vibration upon activation by a voltage controlled oscillator which forms part of a phase-lock loop circuit. The vibrations of the structural member generate electric signals on the receiver film, which feed into a phase comparator. The other input of the phase comparator is the output signal of the voltage controlled oscillator. The phase comparator will output a dc signal proportional to the difference in phase between the two signals. When the structural member becomes damped, the phase comparator will go into saturation, thereby producing a voltage which can activate an alarm signal or other device.

Abstract: An impulse sensor comprises a first Piezo electric disc (25) with two oppositely polarized halves disposed symmetrically about a reference plane including the rib (26) of a thin wall of the transducer container vessel and pressed onto the thin wall, and a second Piezo electric disc (29) with the same polarization for both halves disposed symmetrically about the reference plane and pressed onto a rigid wall of the transducer container vessel. The impulses transversely acting on an impulse receiving member extending from the thin wall generate electric signals of high signal-to-noise ratio from the first Piezo electric disc (25) and electric signals of low signal-to-noise ratio from the second Piezo electric disc (29). The electric signals from the two Piezo electric discs are combined to cancel noises and extract refined signals representing the impulses.

Abstract: Method and apparatus for monitoring temperature along coil sections in a winding of an electromagnetic machine wherein each coil section comprises a plurality of electrical conductors. One or more hollow core conductors are placed in each coil section during manufacture of the coil sections. Before or after the stator core winding is installed, a distributed sensor probe is threaded through selected hollow core conductors for monitoring the temperature along the coil sections.

Abstract: A self monitoring pressure transducer includes a reference chamber, that transmits the pressure through a fluid medium to the flat side of a diaphragm, using a piezoelement, arranged in the reference chamber, as an electrically controllable actor. The piezoelement can modulate the pressure in the reference chamber by a predetermined quantity. The modulation of the measuring signal associated with this pressure modulation permits self-monitoring of the pressure transducer while it is in operation.

Abstract: A piezoelectric load cell which can be utilized for detecting collisions and obstruction of a robot arm end effector includes a force sensing element of metallized polyvinylidene fluoride (PVDF) film. The piezoelectric film sensing element and a resilient support pad are clamped in compression between upper and lower plates. The lower plate has a central recess in its upper face for supporting the support pad and sensing element, while the upper plate has a corresponding central projection formed on its lower face for bearing on the sensing element and support pad. The upper and lower plates are dowelled together for concentric alignment and screwed together. The upper and lower plates are also adapted for mounting between the robot arm wrist and end effector.

Abstract: An electronic oil pressure transducer circuit interfaces a piezoresistive pressure sensor to magnetic needle movement and lamp or electronic instrument control computer for reliable automotive engine oil pressure instrumentation. Circuit design uses standard components suited for automotive under-hood environment. Calibration is performed at the design level, eliminating the need for expensive on-line procedures. Circuit assembly is designed for automated, high-volume production.

Abstract: A rate of ascent monitor for drivers uses a sound transducer with velocity characteristics, preferably a diaphragm type piezoelectric transducer, to sense rate of pressure change, and a threshold detector connected to the transducer to drive an indicator providing a warning of an excessive rate of ascent. A second threshold detector can be used to discriminate between descending and ascending motion. The device can be a compact wrist mounted unit.

Abstract: A sensor is disclosed herein employing a high-sensitivity, high-resolution piezoelectric device for converting physical forces into an electrical signal. An electrical feedback circuit is utilized to cancel the capacitance of piezoelectric crystals so as to provide voltage gain with little increase in noise level. The circuit includes a unity gain amplifier outputting only pure signal gain resulting in an increase in resolution as well as in signal output.

Abstract: Systems including piezoelectric sensor elements advantageously mounted between supporting hard plastic material of various types or other mechanically similar materials. The sensor can further be supported by backup plate structures. Some backup plates show full shoe coverage and others show partial sole coverage. Detachable mounting formed by mechanically interengaging parts allow transducer inserts to be made in a modular manner for use in different sensor shoes or sensor insole pads, thus allowing many more patients to be analyzed and treated through use of the invention. Also disclosed is a digital charge signal integrator circuit.

Abstract: Piezoelectric resonator with maximum sensitivity to external pressure stres.The resonator includes means (2,3) for exerting nonlocalized radial compressive forces uniformly over diametrically opposed peripheral zones of the crystal (1) in which the zones occupy a predetermined sector 2.alpha. of at least approximately 110.degree. and are oriented so that the bisectors (A--A) of the peripheral zones form a predetermined angle .psi. with the crystallographic X axis of the crystal.Depending on the value of .psi., it is possible to minimize or, on the contrary, maximize the sensitivity of the resonator to the external pressure stresses.

Abstract: A support for an elongated piezoelectric pressure sensor, which is general cylindrical in shape is mounted on a hollow support member that has a thickness and strength selected to meet desired conditions. The elongated piezoelectric pressure sensor is wound in a helical depression on the exterior of the support member, and the support member in turn is filled with a potting material having a bulk modulus of elasticity selected to provide a sufficient flexibility so that the elongated piezoelectric sensing element generates signals that have a desired sign characteristic and improved acoustic response.

Abstract: A multi-component dynamometer for measuring forces and torques includes two force introduction plates and pre-oriented transducer elements without housing arranged between them. Each transucer element comprises typically a rectangular plate and two pre-oriented piezoelectric elements fixed thereon, one of these being sensitive to shear in a direction parallel to one edge of the carrier plate and the other being sensitive to pressure in a direction parallel to the normal of the carrier plate. The pre-oriented transducer elements enable the number of piezoelectric elements and electrical connections to be reduced substantially when assembling measuring platforms, as well as the amount of orientation and testing work. The platforms can be made flatter and more rigid, thereby raising the natural frequency. The electronic measuring and evaluation parts can be integrated partially or wholly into the dynamometer.

Abstract: A sensor apparatus includes a pressure sensor, a reference device and a temperature sensor collocated within a common environment. The reference device and the temperature sensor are constructed to have temperature response times matched to the temperature response time of the pressure sensor to compensate for temperature gradients produced either by external heating or by pressure-volume heating.

Abstract: An oscillator employs a single flat piezo-electric transducer as a frequency determining element. The transducer has first, second and third mutually orthagonal axes. The first and second axes lie in a selected one of first and second planes. The first plane is the plane of the transducer, the second plane is at right angles to the first plane. The third axis is perpendicular to the selected plane. The transducer has different modes of excitation in different planes which have different resonant frequencies. The oscillator has a positive feedback loop containing in series a high pass filter and a low pass filter which together [a] determine one selected mode of excitation of the transducer in the selected plane with an associated resonant frequency whereby the transducer resonates in the selected plane at the associated resonant frequency and [b] also prevent the transducer from being excited along the third axis.

Abstract: An oscillating crystal force transducer and method of making the same are provided, the transducer comprising support structure, a plate-shaped piezo-electric crystal having opposed sides and a peripheral edge extending between the opposed sides, and two seating members carried by the support structure and respectively engaging the peripheral edge of the crystal and arranged to apply a force to the crystal along a line extending through the crystal from one of the seating members to the other of the seating members, the support structure comprising a looped spring member having opposed ends spaced from each other to define the mouth of the looped spring member and respectively carrying the seating members whereby the crystal is disposed in the mouth of the looped spring member between the seating members thereof.

Abstract: A pressure sensing transducer comprises a central region which comprises a potting material and which is surrounded by a helix of piezo electric coaxial cable. The transducer includes a barrier that suppresses transmission of external pressure variations to the central region. In addition, the overall radial stiffness of the potting material and barrier is sufficiently low that the electrical signal generated by the coaxial cable have a d.sub.31 polarity (corresponding to axial stretching and contracting of the cable).

Abstract: A piezoelectric sensor adapted for incorporation into a high pressure fuel line employs a pair of piezoelectric transducer elements which are mounted in diametrically opposed bores of a main body. The body forms an axially extending fluid conduit. The main body also has a deformable wall section adjacent the transducer elements. A conductor ring extends the circumference of the main body. The transducer elements electrically connect with the ring so that a pressure pulse traversing the conduit deforms the wall section and produces a mechanical stress on the transducer elements to generate a voltage signal at the conductor ring.

Abstract: An ultrasonic depth gauge 20 for liquids under high pressure is comprised of a transducer assembly 21 and a supporting electronics unit 22. The transducer assembly is mounted into the bottom wall of a storage vessel 12 with its resonating surface directly exposed to the highly pressurized liquid 13 in the vessel. The transducer assembly consists of a conventional transducer element 38 rigidly bonded to the inside wall of a bored out conventional high-pressure plug 30 thereby forming a composite resonator 50. The element and the plug wall resonate as one upon electrical excitation of the element while the transducer element is completely shielded from any exposure to the liquid under high pressure. The composite resonator sends a vibration up to the surface of the liquid where it is reflected back to the composite resonator. The supporting electronics unit measures the vibration round-trip transit time which is proportional to the depth 15 of the liquid.

Abstract: A cylinder pressure transmitter has piezoelectric means to provide an electrical signal corresponding to pressure in a cylinder of an automotive internal combustion engine during engine operation and has electronic means to amplify the signal for transmission to computer control means for use in regulating spark advance to improve engine efficiency and performance and reduce engine knocking. The pressure transmitter has a generally cylindrical body having a chamber open at both ends for attachment to an engine cylinder, has a diaphragm secured over one end of the chamber, and has the piezoelectric means held against the diaphragm with a selected preload compressive force by backing means which are threadedly engaged with the body inside the chamber for adjustment to provide the desired force.

Abstract: A quartz resonator pressure transducer includes a generally disc-shaped resonator section adapted to vibrate in response to an oscillatory signal, a housing having sidewalls which generally circumscribe the resonator section and extend in opposite directions generally normal to the plane of the resonator section, and a web, thinner than the resonator section, joining the housing to the perimeter of the resonator section to define grooves between the sidewalls of the housing and the resonator section on the top and bottom sides of the section.

Abstract: A sensor for scanning physical processes in a combustion chamber of an internal combustion engine includes a pressure-sensitive element formed by two sapphire small parts one of which has a recess and forms a pressure diaphragm to which resistors are applied. The sensor is formed by means of the silicon-on-sapphire technology.

Abstract: A system is provided for determining the pressure exerted on an object passed between two rollers. The system comprises a sensor of pressure-sensitive material and a transmission/receiving device for generating an ultrasonic wave in the sensor and then detecting the reflected pulse received by the sensor. The time difference between the transmission pulse and the pulse received by the sensor is related to the pressure exerted on the object in the nip. Preferably, the sensor consists of a laminated film comprising in sequence: a first layer of electrically conducting material; a layer of polyvinylidene fluoride; a second layer of electrically conducting material having detector regions; a layer of dielectric material; and a third layer of electrically conducting material.

Abstract: A vibrating beam resonator is formed with a unitary isolator mass at each end of the vibratory beam. Isolator springs connected to the unitary masses are joined to mounts. Forces applied to the mounts cause the vibrating beam frequency to vary to enable precise force measurements. With this arrangement, fewer cutting operations are required to produce the vibrating beam resonator than were necessary with known resonators. In a preferred embodiment, a side of the vibratory beam is formed by an edge of the crystal blank from which the resonator is cut to further reduce cutting time. This also permits cuts to be made from only one side of the blank.

Abstract: A tool force sensor assembly (20) generates an electrical signal which is related to the change in force applied by a tool (24) to a workpiece (28) and is indicative of the wear condition or failure of the tool (24). The sensor assembly (20) is mounted in force transmitting relationship between a movable tool support (30, 36) and a nut member (44, 45) which is driven by screw shaft (40, 41). The sensor assembly (20) comprises a plurality of ring-shaped piezoelectric transducers (48) which are held in preselected, circumferentially spaced relationship to each other around the screw shaft (40, 41) by a retainer ring (56, 58) which is sandwiched between a pair of load distribution plates (52, 54). Fasteners (46) extend through each of the transducers (48) and mount the sensor assembly (20) between the nut member (44, 45) and the tool support (30, 36).

Abstract: A transducer comprising a flexible piezoelectric layer as a sensor element for measuring mechanical quantities in hollow bodies, above all pressures in pipes, the opposite sides of this layer being bonded to electrically-conductive contact layers and being connectable via leads to a display and evaluation unit. In order to achieve a high temperature stability in such transducers and to make them suitable for use at temperatures exceeding 80.degree. C., the piezoelectric layer is proposed to consist of wurtzite or sphalerite. One of the electrically-conductive contact layers can be of some heat-resistant, flexible supporting material, for instance flexible metal foil, such as Cu-Be foil, or a sheet of plastic, one or both of whose sides are metallized, and the other electrically-conductive contact layer can be a metal coating applied by evaporation.

Abstract: An improved gas density transducer which compares the resonant frequency of an enclosed, reference tuning fork crystal oscillator with the resonant frequency of a detector tuning fork crystal oscillator exposed to the surrounding gas. The frequency of oscillation of the detector crystal oscillator exposed will vary in accordance with the gas density because of the motional resistance of the gas to vibrations of the tuning fork oscillator. The frequency of the detector oscillator can be compared to the frequency of the reference oscillator to determine the gas density.

Abstract: An oscillator utilizes a piezo-electric transducer as a frequency determining element. The transducer, when unloaded, has a resonant frequency which determines the oscillation frequency and exhibits a pretermined level of amplitude excursion. A clamping mechanism detachably couples the transducer into engagement with a conduit through which fluid flows. This action increases the loading of the transducer and produces a change of resonant frequency, causing the oscillator frequency to change, and also causing the level of amplitude excursion to change. The amount of oscillator frequency change and the change in excursion level have respective values when the fluid flowing in the conduit past the transducer is bubble free which differ from the respective values when the fluid contains bubbles. Circuitry responsive to the changing amplitude values produces an output signal when a selected one of the bubble free and bubble containing conditions is detected.

Abstract: An oscillator utilizes a piezo-electric transducer as a frequency determining element. The transducer, when unloaded, has a resonant frequency which determines the oscillation frequency and exhibits a predetermined level of amplitude excursion. The transducer, when moved into engagement with a conduit through which fluid flows, becomes loaded and exhibits a change of resonant frequency, whereby the oscillator frequency changes, and also exhibits a change in level of amplitude excursion. The amount of oscillator frequency change and the change in excursion level have respective values when the fluid flowing in the conduit past the transducer is bubble free which differ from the respective values when the fluid contains bubbles. Circuitry responsive to at least one of the changing frequency and amplitude values produces a signal when a selected one of the bubble free and bubble containing conditions is detected.

Abstract: A sensor is used for the recognition of coins, which analyses the mintage. The main component of the sensor is a polymeric, elastic material (20) which has piezoelectrical properties. By pressing the minted face of a coin onto the sensory surface (23) a signal is produced corresponding to the high and low points of the mintage, which permits an assessment of the coin by means of the connection of an electronic evaluation unit.

Abstract: A double resonator beam force transducer configured to minimize longitudinal pumping by making the beams vibrate symmetrically. This can be accomplished by making the boundary conditions of the beams symmetrical or, if the boundary conditions are nonsymmetric, then by biasing the beams inwardly or outwardly to compensate for the nonsymmetrical boundary conditions of the beams. In the nonsymmetrical case where the beams would bow outwardly at their fundamental resonant frequency or an odd overtone thereof, an inward bias is provided to minimize longitudinal pumping. In the nonsymmetrical case where the beams would bow inwardly at an even overtone of the fundamental resonant frequency, an outward bias is provided to minimize longitudinal pumping.

Abstract: A sensor for generating a signal in response of a variation at the tactile face. The sensor comprises superposed transmitting and receiving layers, which are provided with electrodes for the supply and pick-up of electrical signals to the transmitting layer and from the receiving layer respectively. With a high acoustic impedance of the boundary medium adjacent to the transmitting layer and a low acoustic impedance of the boundary medium adjacent to the receiving layer or vice versa, the sum of the thicknesses of the transmitting and receiving layers is an odd number of v/4f. With similar impedances, either low or high, of the said boundary media the aforesaid sum is an even number of v/4f. v is the propagation velocity of the acoustic vibration in the material of the transmitting and receiving layers and f the frequency of the signal supplied.

Abstract: A pressure transducer for measuring the internal combustion chamber pressure of an internal combustion engine includes a pair of piezoelectric flat plates loaded in shear mode on opposite sides of a central stamp element connected to the plunger of a pressure responsive membrane, pressure distribution elements bearing externally on the piezoelectric plates, abutment elements bearing externally on the pressure distribution elements, and a prestress spring surrounding the abutment elements and applying compressive forces to the distribution elements and for retaining the piezoelectric plates in place. And, the abutment elements are connected to the housing such that the axial force exerted against the stamp element by the pressure to be measured exerts a thrust on both piezoelectric plates which thrust is absorbed by the abutment elements and transferred to an end of the housing confronting the pressure to be measured.

Abstract: Tactile sensing apparatus for detecting a tactile sense with an object to-be-handled, comprising a plurality of pressure sensing devices, a processor which processes outputs of the pressure sensing devices, and a touch device which contacts with the respective pressure sensing devices in common, whereby information items on a pressure sense, a viscosity sense and a slip sense are simultaneously detected with the outputs of the pressure sensing devices which vary depending upon a direction and a magnitude of a force acting on the touch device.

Abstract: A force and pressure transducer comprises a plate-like crystal. Two separate portions of the crystal are maintained in oscillation at different frequencies by a circuit. The crystal is firmly secured to a solid member in such a manner that deformation in the solid manner, caused by the force or fluid pressure to be measured, results in a secondary force being transmitted to the crystal. This compels the frequency of one of the two oscillating portions of the crystal to change substantially whereas the frequency of the other portion changes only minimally. The difference frequency between the two portions is a highly accurate measure of the force or fluid pressure to be measured.In oscillating crystal transducers hitherto employing plate-like crystals wherein the force to be measured is transmitted along the surface direction, the maximum applicable force has been limited by the ability of the crystal to sustain larger forces.

Abstract: Hoof force detection apparatus having shoe portions adapted for connecting to the hooves of hoofed animals. The apparatus also includes piezoelectric elements mounted on sensor mounting sections which are connected to the shoe portions using flexion joints. The flexion joints allow forces applied to the animal's hooves through the shoe to be accommodated without applying undesirable bending moments and shear forces which would render output signals from the piezoelectric elements unreliable. Preferred forms of shoe-transducer structures include a plurality of spokes extending from shoe portions to centrally positioned sensor mounting sections. Other forms have sensors mounted in the shoe portions. The piezoelectric sensor structures preferably include a ceramic piezoelectric element protected by a cap having a flange. The protective cap and piezoelectric element are held in place by a mounting ring in some preferred embodiments. Backup plates can be used to properly support the sensor structures.

Abstract: The invention relates to a force transducer with at least 100 pC/N sensitivity. The piezo elements of this force transducer are connected rigidly to the force introducing elements, and therefore require no mechanical prestressing. A diaphragm may be provided and is then the only force shunt with a maximum proportion of 5%. The main force flow runs in these transducers through the piezo elements themselves, thereby keeping the pseudo-pyro effect, which is frequently brought about by mechanical shunting, within very narrow limits. Because of bottlenecks in the heat guide path to the piezo elements and the symmetrical construction of the supports, heat transients are also prevented from exerting an appreciable effect on the position of the zero point. This provides zero point stability, which allows accurate measurements in the 0 . . . 1 N range, even where the ambient conditions are unfavorable from the point of view of temperature.

Abstract: The present invention relates to a gasket type pressure sensor mounted on a vibrating body such as a cylinder head of an engine generating vibration derived from knocking and fuel injection, and used to detect pressure fluctuation by means of piezoelectric elements. An object of the present invention is to prevent an oil- and water-leakage from a portion of the gasket type pressure sensor and eliminate caulking and electrical shortcircuiting. This is accomplished by placing a presser metal portion between the piezoelectric elements and the seam of a metal case which encloses them.

Abstract: An electrically variable three terminal monomorphic piezoelectric capacitor is manufactured with thick or thin film hybrid microelectronic circuit technology. A first capacitor plate and a ridge, which substantially surrounds and extends above the first capacitor plate, are formed on the surface of a substrate. A monomorphic piezoelectric wafer having a control plate and a second capacitor plate on opposing surfaces is bonded to the upper surface of the ridge. During bonding, a force is applied at the center of the wafer which fixes a permanent bow in the wafer in the direction of the first capacitor plate. A four terminal monomorphic embodiment and three and four terminal bimorphic embodiments are also described.

Abstract: A pressure sensing apparatus for use in an integrated circuit testing station is disclosed. The testing station includes a probe, a support structure, and lift means for moving an integrated circuit upward toward the probe. The invention specifically consists of a pressure pad secured to the support structure directly above the probe. The pad includes a resilient body portion having a rigid tip. Embedded within the pad is a piezoelectric element having electrical contact leads attached thereto. When the testing station is used, an integrated circuit is moved upward by the lift means toward the probe. As the circuit contacts the probe, it moves the probe upward. As the probe moves upward, it pushes on the pad, causing internal pressures to be generated therein. Such pressures are transmitted to the piezoelectric element which generates electrical impulses proportional to the pressures exerted on the pad.